Zinc-Free Farm Tractor Fluid

ABSTRACT

A lubricating composition comprising an oil of lubricating viscosity; an amine salt of a phosphorus acid ester; a thiadiazole copper corrosion inhibitor; an overbased metal detergent; a boron compound; and at least one friction modifier provides good lubrication of a mechanical device such as a farm tractor, even though such composition is substantially free from zinc dialkyldithiophosphate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. provisional application No. 60/605,115, filed Jun. 29, 2005

BACKGROUND OF THE INVENTION

The present invention relates to lubricants useful for farm tractor fluids, also referred to as tractor hydraulic fluids or lubricants. The fluids are substantially free from zinc salts such as zinc dialkyldithiophosphates.

Farm tractor lubricants are fluids which are called upon to play multiple roles in the lubrication of farm tractors and related equipment. In many instances the same fluid is used to lubricant the crankcase, clutch, transmission, and power take-off components. As a result of exposure to the harsh conditions of the crankcase, the fluid may become contaminated with water and other byproducts of combustion.

For many years, lubricants in general and farm tractor lubricants in particular have contained zinc dialkyldithiophosphates (“ZDPs”) as important components, providing antioxidancy, anti-corrosion activity, antiwear activity and other benefits. However, exposure of such lubricants to water during use can lead to hydrolysis of the ZDP as well as other interactions with metals such as copper and consequent loss of, e.g., corrosion protection for yellow metals.

There are many formulations that have been suggested for use as farm tractor fluids, also known as tractor hydraulic fluids. For example, U.S. Pat. No. 5,843,873, Butke et al., Dec. 1, 1998, discloses lubricants and fluids useful in pressure transmitting applications such as tractor hydraulic fluids. The compositions contain a thiocarbamate and a phosphorus acid or ester or an amine salt thereof, an a surfactant which can be, e.g., glycerol partial esters. The phosphorus compound can be a dialkyl hydrogen phosphite. Another additive which can be present is a dimercaptothiadiazole or a derivative thereof, which can be used as a copper corrosion inhibitor. Overbased materials can also be present, which can be further treated, if desired with other substances such as a boron source.

European Patent Application Publication EP 0 712 924 A, May 22, 1996, discloses oil based compositions which can serve as a functional fluid, in particular, a tractor hydraulic fluid. Components include a compound of the structure

R₁R₂N—C(X)S-Q

(an example of which is (C₄H₉)₂N—C(═S)—S—CH₂CH₂C(═O)—OCH₃), and a sulfur-containing phosphoric acid. A surfactant can also be present. The materials are described as providing good antiwear properties even in the absence of typical zinc compounds such as zinc dialkylthiophosphates. Another additive which can be present is a dimercaptothiadiazole or a derivative thereof, which can be used as a copper corrosion inhibitor. Among the listed surfactants is a borated C₁₆ α-olefin epoxide.

U.S. Pat. No. 5,284,591, Bayles et al., Feb. 8, 1994, discloses a functional fluid (one type of which is a tractor fluid) comprising an overbased calcium sulfonate, a ZDP, a borated epoxide, a carboxylic solubilizer in the form of an ester-salt reaction product of an acylating agent and an alkanol tertiary monoamine, and a sulfurized composition.

U.S. Pat. No. 5,635,459, Stoffa et al., Jun. 3, 1997, discloses borated overbased sulfonates for improved gear performance in functional fluids. The fluid can also contain a ZDP or other EP/antiwear agent, and a borated epoxide. Functional fluids are disclosed to include tractor fluids.

U.S. Pat. No. 5,298,177, Stoffa, Mar. 29, 1994, discloses a functional fluid comprising a triglyceride, a detergent-inhibitor additive, a viscosity modifying additive, and a synthetic oil. The detergent inhibitor can be free from phosphorus and zinc and can include, e.g., a metal passivator which can be an oil-soluble derivative of a dimercaptothiadiazole. The detergent inhibitor may also be a borated complex of an overbased metal sulfonate, carboxylate, or phenate.

The present invention, therefore, solves the problem of hydrolysis of ZDP and resulting deterioration in performance by providing a fluid free from or substantially free from ZDP and other zinc compounds, by including a dithiophosphate ester or salt (other than zinc), a heterocyclic organic compound, and a boron-containing component. The fluid of the invention continues to exhibit acceptable performance. The absence of ZDP can also provide a fluid with improved environmental properties.

SUMMARY OF THE INVENTION

The present invention therefore provides a lubricating composition comprising: (a) an oil of lubricating viscosity; (b) at least one amine salt of a phosphorus acid ester; (c) at least one thiadiazole compound (which may be a copper corrosion inhibitor); (d) at least one overbased metal detergent; (e) at least one boron compound other than an overbased metal detergent; and (f) at least one friction modifier other than a boron compound; said composition being substantially free from zinc dialkyldithiophosphate.

The invention also provides a method for lubricating a mechanical device such as the hydraulic system of a farm tractor, comprising supplying thereto the foregoing lubricating composition.

DETAILED DESCRIPTION OF THE INVENTION

Various preferred features and embodiments will be described below by way of non-limiting illustration.

Oil of Lubricating Viscosity.

One component of the present invention is an oil of lubricating viscosity, which can be present in a major amount, for a lubricant composition, or in a concentrate forming amount, for a concentrate. Suitable oils include natural and synthetic lubricating oils and mixtures thereof. In a fully formulated lubricant, the oil of lubricating viscosity is generally present in a major amount (i.e. an amount greater than 50 percent by weight). Typically, the oil of lubricating viscosity is present in an amount of 75 to 95 percent by weight, and often greater than 80 percent by weight of the composition.

Natural oils useful in making the inventive lubricants and functional fluids include animal oils and vegetable oils as well as mineral lubricating oils such as liquid petroleum oils and solvent-treated or acid-treated mineral lubricating oils of the paraffinic, naphthenic or mixed paraffinic/-naphthenic types which may be further refined by hydrocracking and hydrofinishing processes.

Synthetic lubricating oils include hydrocarbon oils and halo-substituted hydrocarbon oils such as polymerized and interpolymerized olefins, also known as polyalphaolefins; polyphenyls; alkylated diphenyl ethers; alkyl- or dialkylbenzenes; and alkylated diphenyl sulfides; and the derivatives, analogs and homologues thereof. Also included are alkylene oxide polymers and inter-polymers and derivatives thereof, in which the terminal hydroxyl groups may have been modified by esterification or etherification. Also included are esters of dicarboxylic acids with a variety of alcohols, or esters made from C5 to C12 monocarboxylic acids and polyols or polyol ethers. Other synthetic oils include silicon-based oils, liquid esters of phosphorus-containing acids, and polymeric tetrahydrofurans.

Unrefined, refined and rerefined oils, either natural or synthetic, can be used in the lubricants of the present invention. Unrefined oils are those obtained directly from a natural or synthetic source without further purification treatment. Refined oils have been further treated in one or more purification steps to improve one or more properties. They can, for example, be hydrogenated, resulting in oils of improved stability against oxidation.

In one embodiment, the oil of lubricating viscosity is an API Group II, Group III, Group IV, or Group V oil, including a synthetic oil, or mixtures thereof. These are classifications established by the API Base Oil Interchangeability Guidelines. Both Group II and Group III oils contain <0.03 percent sulfur and >99 percent saturates. Group II oils have a viscosity index of 80 to 120, and Group III oils have a viscosity index >120. Polyalphaolefins are categorized as Group IV. The oil can also be an oil derived from hydroisomerization of wax such as slack wax or a Fischer-Tropsch synthesized wax. Group V is encompasses “all others” (except for Group I, which contains >0.03% S and/or <90% saturates and has a viscosity index of 80 to 120).

In one embodiment, at least 50% by weight of the oil of lubricating viscosity is a polyalphaolefin (PAO). Typically, the polyalphaolefins are derived from monomers having from 4 to 30, or from 4 to 20, or from 6 to 16 carbon atoms. Examples of useful PAOs include those derived from 1-decene. These PAOs may have a viscosity of 1.5 to 150 mm²/s (cSt) at 100° C. PAOs are typically hydrogenated materials.

The oils of the present invention can encompass oils of a single viscosity range or a mixture of high viscosity and low viscosity range oils. In a preferred embodiment, the oil exhibits a 100° C. kinematic viscosity of 1 or 2 to 8 or 10 mm²/sec (cSt). The overall lubricant composition is preferably formulated using oil and other components such that the viscosity at 100° C. is 1 or 1.5 to 10 or 15 or 20 mm²/sec and the Brookfield viscosity (ASTM-D-2983) at −40° C. is less than 20 or 15 Pa-s (20,000 cP or 15,000 cP), or less than 10 Pa-s, or even 5 or less.

Amine Salt of Phosphorus Acid Ester

The invention includes an amine salt of a phosphorus acid ester. This material can serve as one or more of an extreme pressure agent, a wear preventing agent. The amine salt of a phosphorus acid ester includes phosphoric acid esters and salts thereof; dialkyldithiophosphoric acid esters and salts thereof; phosphites; and phosphorus-containing carboxylic esters, ethers, and amides; and mixtures thereof.

In one embodiment the phosphorus compound further comprises a sulfur atom in the molecule. In one embodiment the amine salt of the phosphorus compound is ashless, i.e., metal-free (prior to being mixed with other components).

The amine salt of the phosphorus acid ester may comprise any of a variety of chemical structures. In particular, a variety of structures are possible when the phosphorus acid ester compound contains one or more sulfur atoms, that is, when the phosphorus-containing acid is a thiophosphorus acid ester. The thiophosphorus acid esters may be mono- or dithiophosphorus acid esters. Thiophosphorus acid esters are also sometimes referred to as thiophosphoric acids. A phosphorus acid ester may be prepared by reacting a phosphorus compound with an alcohol. Suitable phosphorus compound include phosphorus pentoxide, phosphorus trioxide, phosphorous tetroxide, phosphorus acids, phosphorus esters, and phosphorus sulfides such as phosphorus pentasulfide. Suitable alcohols include those containing up to 30 or to 24, or to 12 carbon atoms, including primary or secondary alcohols such as isopropyl, butyl, amyl, s-amyl, 2-ethylhexyl, hexyl, cyclohexyl, octyl, decyl and oleyl alcohols, as well as any of a variety of commercial alcohol mixtures having, e.g., 8 to 10, 12 to 18, or 18 to 28 carbon atoms. Polyols such as diols may also be used.

In one embodiment, the phosphorus acid ester is a monothiophosphoric acid ester or a monothiophosphate. Monothiophosphates may be prepared by the reaction of a sulfur source with a dihydrocarbyl phosphite. The sulfur source may, for instance, be elemental sulfur, or an organosufide, such as a sulfur coupled olefin or a sulfur coupled dithiophosphate. The preparation of monothiophosphates is disclosed in U.S. Pat. No. 4,755,311 and PCT Publication WO 87/07638, which describe monothiophosphates, sulfur sources, and the process for making monothiophosphates. Monothiophosphates may also be formed in the lubricant blend by adding a dihydrocarbyl phosphite to a lubricating composition containing a sulfur source, such as a sulfurized olefin. The phosphite may react with the sulfur source under blending conditions (i.e., temperatures from about 30° C. to about 100° C. or higher) to form the monothiophosphate salt with an amine which is present in the blend.

In certain embodiments, the phosphorus-containing acid is a dithiophosphoric acid or phosphorodithioic acid. The dithiophosphoric acid may be represented by the formula (RO)₂PSSH wherein each R is independently a hydrocarbyl group containing 3 to 30 carbon atoms. R generally contains up to 18, or to 2, or to 8 carbon atoms. Examples of R include isopropyl, isobutyl, n-butyl, sec-butyl, the various amyl, n-hexyl, methylisobutyl carbinyl, heptyl, 2-ethylhexyl, isooctyl, nonyl, behenyl, decyl, dodecyl, and tridecyl groups. Illustrative lower alkylphenyl R groups include butylphenyl, amylphenyl, and heptylphenyl. Examples of mixtures of R groups include 1-butyl and 1-octyl; 1-pentyl and 2-ethyl-1-hexyl; isobutyl and n-hexyl; isobutyl and isoamyl; 2-propyl and 2-methyl-4-pentyl; isopropyl and sec-butyl; and isopropyl, and isooctyl.

In certain embodiments, the dithiophosphoric acid may be reacted with an epoxide or a glycol and this reaction product further reacted with a phosphorus acid, anhydride, or lower ester. The epoxide is generally an aliphatic epoxide or a styrene oxide. Examples of useful epoxides include ethylene oxide, propylene oxide, butene oxide, octene oxide, dodecene oxide, and styrene oxide. The glycols may be aliphatic glycols having from 1 to 12, or 2 to 6, or 2 or 3 carbon atoms. The dithiophosphoric acids, glycols, epoxides, inorganic phosphorus reagents and methods of reacting the same are described in U.S. Pat. Nos. 3,197,405 and 3,544,465.

The following Examples B-1 and B-2 exemplify the preparation of useful phosphorus acid esters.

EXAMPLE B-1

Phosphorus pentoxide (about 64 grams) is added at about 58° C. over a period of about 45 minutes to about 514 grams of hydroxypropyl O,O-di(4-methyl-2-pentyl)phosphorodithioate (prepared by reacting di(4-methyl-2-pentyl)-phosphorodithioic acid with about 1.3 moles of propylene oxide at about 25° C.). The mixture is heated at about 75° C. for about 2.5 hours, mixed with a diatomaceous earth and filtered at about 70° C. The filtrate contains about 11.8% by weight phosphorus, about 15.2% by weight sulfur, and an acid number of 87 (bromophenol blue).

EXAMPLE B-2

A mixture of about 667 grams of phosphorus pentoxide and the reaction product of about 3514 grams of diisopropyl phosphorodithioic acid with about 986 grams of propylene oxide at about 50° C. is heated at about 85° C. for about 3 hours and filtered. The filtrate contains about 15.3% by weight phosphorus, about 19.6% by weight sulfur, and an acid number of 126 (bromophenol blue).

Acidic phosphoric acid esters may be reacted with ammonia or an amine, including polyamines, to form an ammonium salt. The salts may be formed separately and then the salt of the phosphorus acid ester may be added to the lubricating composition. Alternately, the salts may also be formed in situ when the acidic phosphorus acid ester is blended with other components to form a fully formulated lubricating composition.

The amines which may be suitable for use as the amine salt include primary amines, secondary amines, tertiary amines, and mixtures thereof. The amines include those with at least one hydrocarbyl group, or, in certain embodiments, two or three hydrocarbyl groups. The hydrocarbyl groups may typically contain 2 to 30 carbon atoms, or in another embodiments 8 to 26 or 10 to 20 or 13 to 19 carbon atoms.

Primary amines include ethylamine, propylamine, butylamine, 2-ethylhexylamine, octylamine, and dodecylamine, as well as such fatty amines as n-octylamine, n-decylamine, n-dodecylamine, n-tetradecylamine, n-hexadecylamine, n-octadecylamine and oleyamine. Other useful fatty amines include commercially available fatty amines such as “Armeen®” amines (products available from Akzo Chemicals, Chicago, Ill.), such as Armeen C, Armeen O, Armeen OL, Armeen T, Armeen HT, Armeen S and Armeen SD, wherein the letter designation relates to the fatty group, such as coco, oleyl, tallow, or stearyl groups.

Examples of suitable secondary amines include dimethylamine, diethylamine, dipropylamine, dibutylamine, diamylamine, dihexylamine, diheptylamine, methylethylamine, ethylbutylamine and ethylamylamine. The secondary amines may be cyclic amines such as piperidine, piperazine and morpholine.

The amine may also be a tertiary-aliphatic primary amine. The aliphatic group in this case may be an alkyl group containing 2 to 30, or 6 to 26, or 8 to 24 carbon atoms. Tertiary alkyl amines include monoamines such as tert-butylamine, tert-hexylamine, 1-methyl-1-amino-cyclohexane, tert-octyl-amine, tert-decylamine, tertdodecylamine, tert-tetradecylamine, tert-hexadecylamine, tert-octadecylamine, tert-tetracosanylamine, and tert-octacosanylamine.

Mixtures of amines may also be used in the invention. In one embodiment a useful mixture of amines is “Primene® 81R” and “Primene® JMT.” Primene® 81R and Primene® JMT (both produced and sold by Rohm & Haas) are mixtures of C11 to C14 tertiary alkyl primary amines and C18 to C22 tertiary alkyl primary amines respectively.

Suitable hydrocarbyl amine salts of alkylphosphoric acid of the invention may be represented by the following formula:

wherein R²¹ and R²² are independently hydrogen or hydrocarbyl groups such as alkyl groups; for the phosphorus acid ester, at least one of R²¹ and R²² will be hydrocarbyl. R²¹ and R²² may contain 3 or 4 to 30, or 8 to 25, or 10 to 20, or 13 to 19 carbon atoms. R²³, R²⁴ and R²⁵ can be independently hydrogen or hydrocarbyl groups, such as alkyl branched or linear alkyl chains with 1 to 30, or 4 to 24, or 6 to 20, or 10 to 16 carbon atoms. These R²³, R²⁴ and R²⁵ groups can be branched or linear groups, and in certain embodiments at least one, or alternatively two of R²³, R²⁴ and R²⁵ are hydrogen. Examples of alkyl groups suitable for R²³, R²⁴ and R²⁵ include butyl, sec-butyl, isobutyl, tert-butyl, pentyl, n-hexyl, sec-hexyl, n-octyl, 2-ethylhexyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, octadecenyl, nonodecyl, eicosyl groups and mixtures thereof.

In one embodiment the hydrocarbyl amine salt of an alkylphosphoric acid ester is the reaction product of a C₁₄ to C₁₈ alkylated phosphoric acid with Primene 81R™ (produced and sold by Rohm & Haas) which is a mixture of C₁₁ to C₁₄ tertiary alkyl primary amines. Other amines which may be used include alkyl alkanol amines, dialkanolamines, trialkanolamines such as triethanolamines as well as borated amines as described hereinbelow.

Similarly, hydrocarbyl amine salts of dialkyldithiophosphoric acid esters of the invention may be represented by the formula:

wherein the various R groups are as defined above and R²⁶ and R²⁷ are as defined for R²¹ and R²². In some embodiments R²⁶ and R²⁷ are both hydrocarbyl groups, and they may contain 3 carbon atoms. Examples of hydrocarbyl amine salts of dialkyldithiophosphoric acid esters include the reaction product(s) of heptylated or octylated or nonylated dithiophosphoric acids with ethylene diamine, morpholine, or Primene 81R™, and mixtures thereof.

The amine salt of as used as this component in the present invention may thus comprise a C₈ to C₂₀ alkylamine salt of a mono- or di-alkyl phosphate ester, or mixtures thereof.

The amount of the amine salt of the phosphorus acid ester can be 0.04 to 4 percent by weight of the lubricating composition, or 0.1 to 2, or 0.2 to 1, or 0.3 to 0.8, or 0.4 to 0.5 weight percent. The amounts will be proportionally higher in a concentrate.

Another material of the present invention is thiadiazole compound. This material may, but need not necessarily, serve as a copper corrosion inhibitor, and it is sometimes referred to as such herein. Examples of such materials include dimercaptothiadozoles (“DMTD”) which may typically serve as a metal passivator and/or an anti-wear agent. DMTDs; their preparation are described in greater detail in U.S. Pat. No. 5,298,177, see columns 42 through 47. In summary, the dimercaptothiadiazoles which can be utilized in the present invention typically are soluble forms or derivatives of DMTD. Materials which can be starting materials for the preparation of oil-soluble derivatives containing the dimercaptothiadiazole nucleus can include 2,5-dimercapto-[1,3,4]-thiadiazole, 3,5-dimercapto-[1,2,4]-thiadiazole, 3,4-dimercapto-[1,2,5]-thiadiazole, and 4,-5-dimercapto-[1,2,3]-thiadiazole. Of these the most readily available is 2,5-dimercapto-[1,3,4]-thiadiazole.

DMTDs are conveniently prepared by the reaction of one mole of hydrazine, or a hydrazine salt, with two moles of carbon disulfide in an alkaline medium, followed by acidification. For the preparation of oil-soluble derivatives of DMTD, it is possible to utilize already prepared DMTD or to prepare the DMTD in situ and subsequently adding a material to be reacted with DMTD.

U.S. Pat. Nos. 2,719,125; 2,719,126; and 3,087,937 describe the preparation of various 2,5-bis-(hydrocarbon dithio)-1,3,4-thiadiazoles and 2-hydrocarbyldithio-5-mercapto-[1,3,4]-thiadiazoles. The hydrocarbon group may be aliphatic or aromatic, including cyclic, alicyclic, aralkyl, aryl and alkaryl. Such polysulfides can be represented by the following general formula

wherein R and R′ may be the same or different hydrocarbyl groups which may, generally, be as defined for the R groups of the above hydrocarbyl amine salts, and x and y be integers from 0 to 8, and the sum of x and y is at least 1. Alternatively, in certain embodiments, R′ can be H when y is 0. A process for preparing such derivatives is described in U.S. Pat. No. 2,191,125, comprising reacting DMTD with a suitable sulfenyl chloride or by reacting the dimercapto diathiazole with chlorine and reacting the resulting disulfenyl chloride with a primary or tertiary mercaptan. U.S. Pat. No. 3,087,932 further describes a one-step process for preparing 2,5-bis(hydrocarbyldithio)-1,3,4-thiadiazole. As another variant, carboxylic esters of DMTD are described in U.S. Pat. No. 2,760,933. Similarly, condensation products of alpha-halogenated aliphatic monocarboxylic acids having at least 10 carbon atoms with DMTD are described in U.S. Pat. No. 2,836,564, while U.S. Pat. No. 2,765,289 describes products obtained by reacting DMTD with an aldehyde and a diaryl amine in molar proportions of from about 1:1:1 to about 1:4:4. The DMTD materials may also be present as salts such as amine salts. Further derivatives are also described in greater detail in the aforementioned U.S. Pat. No. 5,298,177.

In one embodiment, the thiazole compound may be the reaction product of a phenol with an aldehyde and a dimercaptothiadiazole. The phenol may be an alkyl phenol wherein the alkyl group contains at least about 6, e.g., 6 to 24, or 6, or 7, to 12 carbon atoms. The aldehyde may be an aldehyde containing 1 to 7 carbon atoms or an aldehyde synthon, such as formaldehyde. In one embodiment, the aldehyde is formaldehyde or paraformaldehyde. The aldehyde, phenol and dimercaptothiadiazole are typically reacted by mixing them at a temperature up to about 150° C. such as 50° C. to 130° C., in molar ratios of 0.5 to 2 moles of phenol and 0.5 to 2 moles of aldehyde per mole of dimercaptothiadiazole. In one embodiment, the three reagents are reacted in equal molar amounts. The product may be described as an alkylhydroxyphenylmethylthio-substituted[1,3,4]-thiadiazole; the alkyl moiety may be, among others, hexyl, heptyl, octyl, or nonyl.

Useful thiadiazole compounds thus may include 2-alkyldithio-5-mercapto-[1,3,4]-thiadiazoles, 2,5-bis(alkyldithio)-[1,3,4]-thiadiazoles, 2-alkyl-hydroxyphenylmethylthio-5-mercapto-[1,3,4]-thiadiazoles, and mixtures thereof.

Another useful DMTD derivative is obtained by reacting DMTD with an oil-soluble dispersant, such as a substantially neutral or acidic carboxylic dispersant, e.g., a succinimide dispersant or a succinic ester dispersant, in a diluent, by heating the mixture above about 100° C. This procedure and the derivatives produced thereby are described in U.S. Pat. No. 4,136,043, as are various types of suitable dispersants.

The amount of the thiadiazole copper corrosion inhibitor can be 0.01 to 5 percent by weight of the composition, depending in part on the identity of the particular compound. For instance, if the thiadiazole compound is as described for the structure shown above, the amount may be 0.01 to 1 percent, or 0.02 to 0.4 or 0.03 to 0.1 percent by weight. Alternatively, if the thiadiazole is reacted with a nitrogen-containing dispersant, the total weight of the combined product may be significantly higher in order to impart the same active thiadiazole chemistry; for instance, 0.1 to 5 percent, or 0.2 to 2 or 0.3 to 1 or 0.4 to 0.6 percent by weight. The amounts will be proportionally higher in a concentrate.

Another component of the present invention is a detergent. Detergents as used herein are metal salts of organic acids and are well-known from such publications as US 2004-0102335 and references cited therein. The organic acid portion of the detergent is typically a sulfonate, carboxylate, phenate, salicylate, or salixarate. The metal portion of the detergent is typically an alkali or alkaline earth metal. Suitable metals include sodium, calcium, potassium and magnesium.

Suitable overbased organic salts include sulfonate salts having a substantially oleophilic character and which are formed from organic materials. Organic sulfonates are well known materials in the lubricant and detergent arts. The sulfonate compound can contain on average 10 to 40 carbon atoms, for instance, 12 to 36 carbon atoms or 14 to 32 carbon atoms. Similarly, the phenates, salicylates, salixarates, and carboxylates have a substantially oleophilic character.

While the present invention allows for the carbon atoms to be either aromatic or in paraffinic configuration, it is common that alkylated aromatics be employed. While naphthalene based materials may be employed, the aromatic material is typically based on benzene.

Suitable compositions thus include overbased monosulfonated alkylated benzene, such as monoalkylated benzene. Typically, alkyl benzene fractions are obtained from still bottom sources and are mono- or di-alkylated.

In certain embodiments, a mixture of mono-alkylated aromatics (benzene) are utilized to obtain the mono-alkylated salt (benzene sulfonate). Mixtures wherein a substantial portion of the composition contains polymers of propylene as the source of the alkyl groups can also be used to assist in the solubility of the salt. The use of mono-functional (e.g., mono-sulfonated) materials can be used to avoid crosslinking of the molecules with less precipitation of the salt from the lubricant.

The detergents are typically “overbased.” By overbasing, it is meant that a stoichiometric excess of the metal is present over that required to neutralize the anion of the salt, typically facilitated by the addition of carbon dioxide. The excess metal from overbasing has the effect of neutralizing acids which may build up in the lubricant, as well as increasing the dynamic coefficient of friction. Typically, the excess metal will be present over that which is required to neutralize the anion at in the ratio of up to 30:1, such as 1.5:1 to 20:1 or 5:1 to 18:1 on an equivalent basis.

The amount of the overbased metal detergent used in the composition is typically 0.05 to 5 or to 6 weight percent on an oil free basis, for instance, 0.1 to 2 percent or 0.2 to 1.0 percent, or in other embodiments 1 to 5 percent or 2 to 4 percent. The overbased salt as supplied often includes 40% to 50% diluent oil and with a total base number (TBN) of 10 to 600 or to 800 on an oil free basis, or a proportionally lower TBN when calculated including the diluent oil. The detergent can be post-treated with such agents as borating agents. Borated and non-borated overbased detergents are also described in U.S. Pat. Nos. 5,403,501 and 4,792,410 and references cited therein.

Another component of the present invention is a boron compound. The boron compound should be soluble or dispersible in the lubricating compositions. The boron compound is also to be considered and accounted for separately from any borated detergent, described above. The actual chemical identity of the boron compound can be quite diverse. Suitable materials include borated fatty epoxides, known from Canadian Patent No. 1,188,704. These oil-soluble boron-containing compositions can be prepared by reacting boric acid (in any of its various forms) or boron trioxide with at least a fatty epoxide of the general formula

wherein the R groups are hydrogen or aliphatic radicals or which may together form cyclic groups. The fatty epoxide generally contains at least 8 carbon atoms to provide a measure of oil solubility. These materials are often referred to as borated epoxides, and they are described in detail in U.S. Pat. No. 4,584,115. These are generally prepared by reacting an epoxide with boric acid or boron trioxide. Borated epoxides thus are not themselves epoxides but are the boron-containing reaction products of epoxides. The epoxides can be, for example, commercial mixtures of C₁₄₋₁₆ or C₁₄₋₁₈ epoxides, which can be purchased from Elf-Atochem or Union Carbide and which can be prepared, in turn, from the corresponding olefins by known methods. Purified epoxy compounds such as 1,2-epoxyhexadecane can be purchased from Aldrich Chemicals. The borated epoxides are prepared by blending the boron source and the epoxide and heating until the desired reaction has occurred. One suitable borated epoxide is the borated epoxide of a predominantly 16 carbon olefin.

Other types of organic borate esters can be employed, such as are known in the art and described, for instance, in U.S. Pat. No. 5,883,057 and U.S. patent application 2005 0014656. Such borate esters may be prepared by reacting of one or more boron compounds with one or more alcohols. In some embodiments the alcohols contain 6 to 30, or 8 to 24 carbon atoms. The borate esters may be of various formulas including

wherein each R is independently hydrogen or a hydrocarbyl group containing 2 to 24 carbon atoms, provided that at least one R is a hydrocarbyl group. The R groups may also be aliphatic groups of 4 to 6 carbon atoms and in one embodiment all the R groups are aliphatic groups. Among suitable trihydrocarbyl borates are triethyl borate, tripropyl borate, triisopropyl borate, tributyl borate, tripentyl borate, trihexyl borate, tricyclohexyl borate, trioctyl borate, triisooctyl borate, tridecyl borate, tri(C₈₋₁₀) borate, tri(C₁₂₋₁₅ borate) and oleyl borate. The borate esters can be prepared by reacting 1 to 3 moles of alcohol ROH with 1 mole of orthoboric acid H₃BO₃, typically at a temperature of above 100° C. in order to remove of water of condensation.

The length of the alkyl groups in any such borate esters can be varied to obtain desired performance, e.g., solubility or lubricity. Also, partial borate esters can be used. Organic borate salts can also be used.

Suitable boron compounds also include borated amines, which are generally known from U.S. Pat. No. 4,622,158. Borated amines (including borated alkoxylated fatty amines) are conveniently prepared by the reaction of a boron compound, as described above, with the corresponding amines. The amine can be a simple fatty amine or a hydroxy-containing amine. Among the amines useful in preparing the borated amines are commercial alkoxylated fatty amines known by the trademark Ethomeen™ and available from Akzo Nobel. Representative examples of these materials is Ethomeen™ C/12 (bis[2-hydroxyethyl]-coco-amine); Ethomeen™ C/20 (polyoxyethylene[10]cocoamine); Ethomeen™ S/12 (bis[2-hydroxyethyl]soyamine); Ethomeen™ T/12 (bis[2-hydroxyethyl]-tallow-amine); Ethomeen™ T/15 (polyoxyethylene-[5]tallowamine); Ethomeen™ 0/12 (bis[2-hydroxyethyl]oleyl-amine); Ethomeen™ 18/12 (bis[2-hydroxyethyl]octadecylamine); and Ethomeen™ 18/25 (polyoxyethyl-ene[15]-octadecylamine). Fatty amines and ethoxylated fatty amines are also described in U.S. Pat. No. 4,741,848.

The boron compound can also be a borated fatty acid ester, e.g., a borated fatty ester of glycerol. Such material can be prepared by borating a fatty acid ester of glycerol with boric acid with removal of the water of reaction.

In one embodiment, the boron compound is a borated dispersant, such as a borated nitrogen-containing dispersant. Typically, a borated dispersant contains 0.1% to 5%, or 0.5% to 4%, or 0.7% to 3% by weight boron. In one embodiment, the borated dispersant is a borated acylated amine, such as a borated succinimide dispersant. Borated dispersants are described in U.S. Pat. Nos. 3,000,916; 3,087,936; 3,254,025; 3,282,955; 3,313,727; 3,491,025; 3,533,945; 3,666,662 and 4,925,983. Borated dispersant are prepared by reaction of one or more dispersant with one or more boron compounds. The dispersants include acylated amines, carboxylic esters, Mannich reaction products, hydrocarbyl substituted amines, ethoxylated amines, and mixtures thereof.

Acylated amines include reaction products of one or more carboxylic acylating agent and one or more amine. The carboxylic acylating agents include C₈₋₃₀ fatty acids, C₁₄₋₂₀ isoaliphatic acids, C₁₈₋₄₄ dimer acids, addition dicarboxylic acids, trimer acids, addition tricarboxylic acids, and hydrocarbyl substituted carboxylic acylating agents. The hydrocarbyl substituted carboxylic acylating agents are prepared by a reaction of an olefin or polyalkene with an unsaturated carboxylic reagent, such as maleic anhydride. The amines may be any of those described above or a polyamine, such as an alkylenepolyamine or a condensed polyamine. Acylated amines, their intermediates and methods for preparing the same are described in U.S. Pat. Nos. 3,219,666; 4,234,435; 4,952,328; 4,938,881; 4,957,649; 4,904,401; and 5,053,152.

Carboxylic ester dispersants are prepared by reacting a carboxylic acylating agent with an organic hydroxy compound and optionally an amine. Suitable alcohols include polyhydric alcohols, such pentaerythritol. Carboxylic ester dispersant is described in U.S. Pat. Nos. 3,522,179 and 4,234,435

In another embodiment, the dispersant may be a hydrocarbyl-substituted amine, such as are disclosed in U.S. Pat. Nos. 3,275,554; 3,438,757; 3,454,555; 3,565,804; 3,755,433; and 3,822,289. Typically, hydrocarbyl substituted amines are prepared by reacting olefins and olefin polymers, with amines (mono- or polyamines). The amine may be, for example, an alkylenepolyamine.

In another embodiment, the dispersant may be a Mannich dispersant. Mannich dispersants are generally formed by the reaction of an aldehyde, such as formaldehyde or paraformaldehyde, an amine such as a polyamine (e.g., a polyalkylenepolyamine), and a substituted hydroxyaromatic compound. The amounts of the reagents are typically in a mole ratio of hydroxyaromatic compound to formaldehyde to amine of (1:1:1) to (1:3:3). The hydroxyaromatic compound is generally an alkyl substituted hydroxyaromatic compound. Mannich dispersants are described in the following patents: U.S. Pat. No. 3,980,569; U.S. Pat. No. 3,877,899; and U.S. Pat. No. 4,454,059.

The boron compound of the present invention can also be a reaction product of a dialkanolamine and boric acid, further reacted with a C₈ to C₂₀ fatty acid, that is to say, long chain alkenyl amide borates. Specific examples include the reaction product of mixed fatty acids such as tall oil acids with diethanolamine and boric acid. (Tall oil acids are commercially available mixtures of acids, predominantly oleic and linoleic acids, containing also residual rosin acids or tallow acids.) In yet another embodiment, the boron compound can be the reaction product of a borating agent such as boric acid with a condensation product of a fatty acid (such as stearic acid or isostearic acid) with a polyamine such as tetraethylenepentamine. Such condensation products are described, for instance, in U.S. Patent Application 2005 0014656, and may be in the form of an amide, am imidazoline, or mixtures thereof.

In another embodiment, the boron compound can be an alkali or mixed alkali metal and alkaline earth metal borate. These metal borates can be hydrated particulate metal borates, which are available commercially and are known in the art from U.S. Pat. Nos. 3,997,454; 3,819,521; 3,853,772; 3,907,601; 3,997,454; and 4,089,790.

The amount of the boron compound will typically be 0.05 to 2 weight percent. The desired amount will, naturally, depend to some extent on the particular boron compound and the amount of boron present in such compound. Typical amounts, for borated dispersants or other boron-containing materials, can also be 0.08 to 1 percent or 0.1 to 0.8 percent or 0.15 to 0.7 percent or 0.2 to 0.5 percent. Alternatively expressed, the amount of the boron compound can be sufficient to provide 40 to 4000 parts per million by weight boron to the composition, or 100 to 1000 or 200 to 800 parts per million.

The lubricating composition of the present invention will also contain at least one friction modifier. Since some of the above-described boron compounds can themselves function as friction modifiers, the present compositions will normally contain a friction modifier other than or in addition to a boron compound, such that any of the boron-containing materials will not be counted as one of the required friction modifiers. Friction modifiers are well known to those skilled in the art. A useful list of friction modifiers is included in U.S. Pat. No. 4,792,410. Suitable friction modifiers include: (i) fatty phosphites; (ii) fatty acid amides; (iii) fatty epoxides; (iv) fatty amines; (v) fatty esters (e.g, glycerol esters, that is, fatty acid glycerides); (vi) alkoxylated fatty amines; (vii) metal salts of fatty acids; (viii) sulfurized olefins; (ix) fatty imidazolines; (x) condensation products of carboxylic acids and polyalkylene-polyamines; (xi) metal salts of alkyl salicylates; (xii) amine salts of alkylphosphoric acids; and mixtures thereof.

Representatives of each of these types of friction modifiers are known and are commercially available. For instance, (i) fatty phosphites, also referred to as fatty alkyl hydrogen phosphites, are generally of the formula (RO)₂PHO. Dialkyl phosphite, as shown in the preceding formula, is typically present with a minor amount of monoalkyl phosphite of the formula (RO)(HO)PHO. In these structures, the term “R” is conventionally referred to as an alkyl group. It is, of course, possible that the alkyl is actually alkenyl and thus the terms “alkyl” and “alkylated,” as used herein, will embrace other than saturated alkyl groups within the phosphite. The phosphite will normally have sufficient hydrocarbyl groups of sufficient length to render the phosphite substantially oleophilic, e.g., 8 to 24 or 12 to 22 or 16 to 20 carbon atoms in each group. The hydrocarbyl groups can be substantially unbranched. Many suitable phosphites are available commercially and may be synthesized as described in U.S. Pat. No. 4,752,416. In one embodiment the fatty phosphite can be formed from oleyl groups, thus having 18 carbon atoms in each fatty radical.

The (vi) alkoxylated fatty amines, and (iv) fatty amines themselves (such as oleylamine) are generally useful as friction modifiers in this invention. Such amines are commercially available, as described above for borated fatty amines. Among suitable amines are secondary or tertiary amine represented by the formula R¹R²NR³ where R¹ and R² are each independently an alkyl group of at least 6 carbon atoms and R³ is hydrogen, a hydrocarbyl group, a hydroxyl-containing alkyl group, or an amine-containing alkyl group. These materials are described in copending U.S. application Ser. No. 10/968,417 filed Oct. 19, 2004.

Fatty acid esters, such as those of glycerol (v) can be used as friction modifiers. These materials can be prepared by a variety of methods well known in the art. Many of these esters, such as glycerol monooleate and glycerol tallowate, are manufactured on a commercial scale. The esters useful are oil-soluble and can be prepared from C₈ to C₂₂ fatty acids or mixtures thereof such as are found in natural products and as are described in greater detail below. Fatty acid monoesters of glycerol are suitable, and mixtures of mono- and diesters may also be used. For example, commercial glycerol monooleate may contain a mixture of 45% to 55% by weight monoester and 55% to 45% diester. Other fatty esters, such as pentaerythritol monooleate or other partial esters of pentaerythritol or other polyols, are also contemplated.

Fatty acids can be used in preparing the above glycerol esters; they can also be used in preparing their (vii) metal salts, (ii) amides, and (ix) imidazolines, any of which can also be used as friction modifiers. Suitable fatty acids include those containing 6 to 24 carbon atoms, e.g., 8 to 18. The acids can be branched or straight-chain, saturated or unsaturated. Suitable acids include 2-ethylhexanoic, decanoic, oleic, stearic, isostearic, palmitic, myristic, palmitoleic, linoleic, lauric, and linolenic acids, and the acids from the natural products tallow, palm oil, olive oil, peanut oil, corn oil, and Neat's foot oil. A particularly preferred acid is oleic acid. Suitable metal salts of such acids include zinc and calcium salts, although zinc salts may be avoided of a low zinc composition is desired. Examples are overbased calcium salts and basic oleic acid-zinc salt complexes which can be represented by the general formula Zn₄Oleate₃O₁. Suitable amides include those prepared by condensation with ammonia or with primary or secondary amines such as diethylamine and diethanolamine.

Fatty imidazolines (ix) are the cyclic condensation product of an acid with a diamine or polyamine such as a polyethylenepolyamine. The imidazolines are generally represented by the structure

where R is an alkyl group and R′ is hydrogen or a hydrocarbyl group or a substituted hydrocarbyl group, including —(CH₂CH₂NH)n groups. In one embodiment the friction modifier can be the condensation product of a C₈ to C₂₄ fatty acid with a polyalkylene polyamine, and in particular, the product of isostearic acid with tetraethylenepentamine. The condensation products of carboxylic acids and polyalkyleneamines (x) may generally be imidazolines or amides.

Sulfurized olefins (vii) are well known commercial materials used as friction modifiers. They may be prepared in accordance with the detailed teachings of U.S. Pat. Nos. 4,957,651 and 4,959,168. Described therein is a cosulfurized mixture of 2 or more reactants selected from the group consisting of (1) at least one fatty acid ester of a polyhydric alcohol, (2) at least one fatty acid, (3) at least one olefin, and (4) at least one fatty acid ester of a monohydric alcohol. Reactant (3), the olefin component, comprises at least one olefin. This olefin can be an aliphatic olefin, which usually will contain 4 to 40 carbon atoms, or 8 to 36 carbon atoms. Terminal olefins, or alpha-olefins, are suitable, especially those having from 12 to 20 carbon atoms. Mixtures of these olefins are commercially available, and such mixtures may be used.

Metal salts of alkyl salicylates (xi) include calcium and other salts of long chain (e.g. C₁₂ to C₁₆) alkyl-substituted salicylic acids.

Amine salts of alkylphosphoric acids (xii) include salts of oleyl and other long chain esters of phosphoric acid, with amines as described herein. Useful amines in this regard are tertiary-aliphatic primary amines, some of which are sold under the tradename Primene™. In certain embodiments the amines are non-branched, since it is believed that amines with non-branched hydrocarbyl groups may provide superior friction performance.

The amount of the friction modifier is generally 0.1 to 10 percent by weight of the lubricating composition, preferably 0.2 to 4 or 0.3 to 2 or 0.5 to 1.5 percent.

An optional component of the present invention is a viscosity modifier. Viscosity modifiers (VM) and dispersant viscosity modifiers (DVM) are well known. Examples of VMs and DVMs are polymethacrylates, polyacrylates, polyolefins, styrene-maleic ester copolymers, and similar polymeric substances including homopolymers, copolymers and graft copolymers. Examples of commercially available VMs, DVMs and their chemical types include polyisobutylenes, olefin copolymers, hydrogenated styrene-diene copolymers, styrene/maleate copolymers, which are dispersant copolymers, polymethacrylates, some of which have dispersant properties, olefin-graft-polymethacrylate polymers, and hydrogenated polyisoprene star polymers. Recent summaries of viscosity modifiers can be found in U.S. Pat. Nos. 5,157,088, 5,256,752 and 5,395,539. The VMs and/or DVMs may be incorporated into the fully-formulated compositions, if desired, at a level of up to 15% by weight or greater, such as 1 to 12% or 3 to 10%.

Other materials can optionally be included in the compositions of the present invention, provided that they are not incompatible with the afore-mentioned required components or specifications. Such materials include antioxidants (that is, oxidation inhibitors), including hindered phenolic antioxidants (e.g., di-t-butylphenol), secondary aromatic amine antioxidants (e.g., mono- and/or dinonyl diphenylamines), sulfurized phenolic antioxidants, oil-soluble copper compounds, phosphorus-containing antioxidants, organic sulfides, disulfides, and polysulfides. Other optional components include seal swell compositions, such as isodecyl sulfolane or phthalate esters, which are designed to keep seals pliable. Also permissible are pour point depressants, such as alkylnaphthalenes, polymethacrylates, vinyl acetate/fumarate or /maleate copolymers, and styrene/maleate copolymers. These optional materials are known to those skilled in the art, are generally commercially available, and are described in greater detail in published European Patent Application 761,805. Also included can be known materials such as corrosion inhibitors, rust inhibitors such as acids and anhydrides (e.g., polyisobutene succinic acid or anhydride), dyes, fluidizing agents, odor masking agents, and antifoam agents.

The formulations of the present invention permit the successful lubrication of mechanical devices such as farm tractors without the necessity of using such zinc salts as zinc dialkyldithiophosphates (ZDPs). While ZDPs normally provide antioxidancy, anti-corrosion activity, antiwear activity and other benefits, the compositions of the present invention are typically substantially free from ZDPs. By “substantially free from ZDP” it is meant that the formulation is prepared without the intentional addition of any ZDP, or alternatively, only a very small amount of ZDP. For example, the formulations may contain less than 0.5 percent by weight ZDP or 0.005 to 0.3 percent or 0.01 to 0.1 or 0.001 to 0.05 percent or less of ZDPs. In certain embodiments, the formulations are substantially free from zinc compounds of any type, thus containing, e.g., less than 0.05 percent by weight Zn or 0.0005 to 0.03 percent or 0.001 to 0.01 or 0.0001 to 0.005 percent or less of Zn.

The ZDPs (which are present in only a low amount or are substantially absent) may be represented by the formula

In this formula, the R⁸ and R⁹ groups are hydrocarbyl groups typically alkyl, cycloalkyl, aralkyl or alkaryl group having 3 to 20 carbon atoms, such as 3 to 16 carbon atoms or up to 13 carbon atoms, e.g., 3 to 12 carbon atoms. The alcohols which are used to provide the R⁸ and R⁹ groups can be one or more primary alcohols, one or more secondary alcohols, or a mixture of secondary alcohol and primary alcohol. A mixture of two secondary alcohols such as isopropanol and 4-methyl-2-pentanol are often used in preparing ZDPs.

As used herein, the term “hydrocarbyl substituent” or “hydrocarbyl group” is used in its ordinary sense, which is well-known to those skilled in the art. Specifically, it refers to a group having a carbon atom directly attached to the remainder of the molecule and having predominantly hydrocarbon character. Examples of hydrocarbyl groups include:

hydrocarbon substituents, that is, aliphatic (e.g., alkyl or alkenyl), alicyclic (e.g., cycloalkyl, cycloalkenyl) substituents, and aromatic-, aliphatic-, and alicyclic-substituted aromatic substituents, as well as cyclic substituents wherein the ring is completed through another portion of the molecule (e.g., two substituents together form a ring);

substituted hydrocarbon substituents, that is, substituents containing non-hydrocarbon groups which, in the context of this invention, do not alter the predominantly hydrocarbon nature of the substituent (e.g., halo (especially chloro and fluoro), hydroxy, alkoxy, mercapto, alkylmercapto, nitro, nitroso, and sulfoxy);

hetero substituents, that is, substituents which, while having a predominantly hydrocarbon character, in the context of this invention, contain other than carbon in a ring or chain otherwise composed of carbon atoms. Heteroatoms include sulfur, oxygen, nitrogen, and encompass substituents as pyridyl, furyl, thienyl and imidazolyl. In general, no more than two, preferably no more than one, non-hydrocarbon substituent will be present for every ten carbon atoms in the hydrocarbyl group; typically, there will be no non-hydrocarbon substituents in the hydrocarbyl group.

It is known that some of the materials described above may interact in the final formulation, so that the components of the final formulation may be different from those that are initially added. For instance, metal ions (of, e.g., a detergent) can migrate to other acidic or anionic sites of other molecules. The products formed thereby, including the products formed upon employing the composition of the present invention in its intended use, may not be susceptible of easy description. Nevertheless, all such modifications and reaction products are included within the scope of the present invention; the present invention encompasses the composition prepared by admixing the components described above.

EXAMPLES

Lubricant compositions are prepared from the components listed in the following Tables:

TABLE 1 Example 1: Component Amount, % Borated succinimide dispersant, including 33% oil, 0.5 1.9% B (boron source) Dispersant/corrosion inhibitor comprising DMTD reacted 1.0 with an ester dispersant, containing about 10% DMTD, 49% oil C₁₂₋₁₄ alkyl amine salt of mono and diesters of 0.4 phosphoric acid (extreme pressure agent) Glycerol monooleate (commercial grade) (friction 0.5 modifier) Oleamide (friction modifier) 0.35 Tall oil acid, product with diethanolamine and boric 0.2 acid (antiwear agent, boron source) Dibutyl hydrogen phosphite (anti-wear agent) 0.25 Di-t-butyl phenol (antioxidant) 0.2 Calcium alklbenzenesulfonate detergent, including 0.8 42% oil, 400 TBN (detergent) Oil of lubricating viscosity balance

TABLE 2 Component Ex 2 Ex 3 Ex 4 Ex 5 Ex 6 Ex 7 Ex 8 Borated succininimide 0.25 0.25 0.25 0.25 0.25 0.25 0.25 dispersant as in Ex. 1 Oleylamine friction modifier 0.11 0.11 0.11 0.11 0.11 0.11 0.15 Alkyl amine salt of phosphoric 0.5 0.5 0.5 0.5 0.5 0.5 0.45 ester as in Ex. 1 Glycerol monooleate (f.m.) 0.5 0.5 0.5 0.5 0.5 0.5 0.5 (Bis-t-nonyldithio)thiadiazole 0.02 0.02 0.02 0.02 0.02 0.02 0 Heptylhydroxyphenylthio 0.03 0.03 0.03 0.03 0.03 0.03 0.03 substituted thiadiazole (including 20% oil) Antifoam agent (commercial) 0.02 0.02 0.02 0.02 0.02 0.02 0 Tall oil acid product as in Ex 1 0.25 0.25 0.25 0.25 0.25 0.25 0 Various overbased calcium 0.5 0.5 0.5 0.55 0.46 1.1 1.1 sulfonate and/or phenate detergents, optionally borated (including 39 to 52% oil) Oil of lubricating viscosity balance

Certain of the above identified formulations are tested according to John Deere published test procedures JDQ 84, 95, and 96, described in greater detail below. Results are shown in the following table:

TABLE 3 Test - JDQ- Ex 1 Ex 2 Ex 3 Ex 4 Ex 5 Ex 6 Ex 7 Ex 8 84: % flow decrease 1.4 — — 0 — — — — Cu, ppm drain 13 — — 9 — — — — Fe, ppm drain 7 — — 20 — — — — Assessment Pass — —  Pass^(a) — — — — 95: Average rating 9.75 9.33 9.83 9.75 9.08 — — — Spiral bevel Rating 9 9 8 9 8 — — — N Sun gear, μm 5.9 6.1 18.5 3.8 24.1 — — — S Sun gear, μm 5.4 4.6 4.3 3.4 20.5 — — — Assessment Pass Pass Pass Pass Pass — — — 96: 10000 cy/capacity 323 341 — — — — — — /variation 69 54 — — — — — — 20000 cy/capacity 340 345 — — — — — — /variation 34 28 — — — — — — 30000 cy/capacity 330 334 — — — — — — /variation 19 25 — — — — — — Assessment Pass Pass — — — — — — —: not determined ^(a)increase in pressure noted

The JDQ-84 dynamic corrosion test evaluates whether oils, when contaminated with limited amounts of water, can still serve as suitable fluids for pumps found on agricultural equipment. After running the test oil through an axial piston pump at 82° C., 34.5 MPa, 1.5 L/sec, for 25 hours, 1% water is added to the oil and the test continued for an additional 200 hours. Reduction in flow, if any, is reported, as well as the presence of Cu and Fe in the drain fluid. The samples tested pass this test.

The JDQ-95 test measures a fluid's antiwear capability as measured in tractor spiral bevel and final drive gear sets. A modified front drive axle assembly is used as the test device. The test is conducted using new spiral bevel ring gear and pinions, final drive sun pinions, and associated planet pinion gears. After 74 hours total testing with the test fluid, the unit is drained and the North and South sun pinion gear teeth are measured for wear, reported in μm (originally measured as micro-inches) and a visual rating on a scale of 1-10 is assigned. A spiral bevel rating of 7 or higher is considered a passing result. The “average rating” is determined from a total of 6 distress merit ratings on both the ring gear and drive pinion. The samples examined pass this test.

The JDQ-96 test assesses the effect of test oil on brake noise and brake capacity compared to that of a reference oil. The test is run at 10,000, 20,000, and 30,000 cycles. Results are presented as torque (arbitrary units, in thousands) as well as variation in torque, that is, variability, in the same units, which is a measure of “chatter.” In this test, a reference material exhibits a value of 333,913 at 30,000 cycles with a variation of 69,178. The samples tested provide very strong passing values.

While the lubricant as described herein may be principally used for lubricating the hydraulic system of a farm tractor, it may also be used for lubricating other mechanical devices such as gears, gear boxes, transmissions for automobiles and other vehicles, including manual transmissions, automatic transmissions, continuously variable transmissions, traction drives, dual clutch transmissions, and transmissions for hybrid (e.g., gasoline and electric) vehicles, as well as other devices such as wind turbines and other machinery. The composition may be used as, or as a part of, a grease or a non-grease lubricant.

Each of the documents referred to above is incorporated herein by reference. Except in the Examples, or where otherwise explicitly indicated, all numerical quantities in this description specifying amounts of materials, reaction conditions, molecular weights, number of carbon atoms, and the like, are to be understood as modified by the word “about.” Unless otherwise indicated, each chemical or composition referred to herein should be interpreted as being a commercial grade material which may contain the isomers, by-products, derivatives, and other such materials which are normally understood to be present in the commercial grade. However, the amount of each chemical component is presented exclusive of any solvent or diluent oil, which may be customarily present in the commercial material, unless otherwise indicated. It is to be understood that the upper and lower amount, range, and ratio limits set forth herein may be independently combined. Similarly, the ranges and amounts for each element of the invention can be used together with ranges or amounts for any of the other elements. As used herein, the expression “consisting essentially of” permits the inclusion of substances that do not materially affect the basic and novel characteristics of the composition under consideration. 

1. A method for lubricating the hydraulic system of a farm tractor, comprising supplying thereto a lubricating composition comprising: (a) an oil of lubricating viscosity; (b) at least one amine salt of a phosphorus acid ester; (c) at least one thiadiazole compound; (d) at least one overbased metal detergent; (e) at least one boron compound other than an overbased metal detergent; (f) at least one friction modifier other than a boron compound; said composition being substantially free from zinc dialkyldithiophosphate.
 2. The method of claim 1 wherein the amine salt of (b) comprises a C₈ to C₂₀ alkylamine salt of a mono- or di-alkyl phosphate ester or mixtures thereof.
 3. The method of claim 1 wherein the amount of the amine salt of (b) is about 0.04 to about 4 percent by weight.
 4. The method of claim 1 wherein the thiadiazole compound of (c) is selected from the group consisting of 2-alkyldithio-5-mercapto-[1,3,4]-thiadiazoles, 2,5-bis(alkyldithio)-[1,3,4]-thiadiazoles, 2-alkylhydroxyphenyl-methylthio-5-mercapto-[1,3,4]-thiadiazoles, and mixtures thereof.
 5. The method of claim 1 wherein the thiadiazole compound of (c) comprises the reaction product of 2,5-dimercapto-[1,3,4]-thiadiazole with a nitrogen-containing dispersant.
 6. The method of claim 1 wherein the amount of the thiadiazole compound of (c) is about 0.01 to about 5 percent by weight.
 7. The method of claim 1 wherein the overbased metal detergent (d) comprises a carbonated overbased metal sulfonate.
 8. The method of claim 1 wherein the amount of the overbased metal detergent is about 0.05 to about 6 percent by weight.
 9. The method of claim 1 wherein the boron compound of component (e) comprises the reaction product of a dialkanolamine and boric acid, further reacted with a C₈ to C₂₀ fatty acid.
 10. The method of claim 1 wherein component (e) comprises a borated nitrogen-containing dispersant.
 11. The method of claim 1 wherein component (e) comprises a borated ethoxylated amine.
 12. The method of claim 1 wherein the amount of component (e) is about 0.05 to about 2 percent by weight.
 13. The method of claim 1 wherein the amount of component (e) is sufficient to provide about 40 to about 4000 ppm B to the composition.
 14. The method of claim 1 wherein the friction modifier of (f) is selected from the group consisting of fatty acid glycerides, fatty acid amides, fatty alkyl amines, polyoxyalkylene fatty alkyl amines, fatty alkyl hydrogen phosphites, pentaerythritol monooleate, and mixtures thereof.
 15. The method of claim 1 wherein the amount of the friction modifier is about 0.1 to about 10 weight percent.
 16. The method of claim 1 further comprising at least one additional additive selected from the group consisting of viscosity modifiers, pour point depressants, antioxidants, rust inhibitors, seal swell compositions, and anti-foam agents.
 17. The method of claim 1, wherein the lubricating composition is prepared by admixing the components of claim
 1. 